The present invention relates to an electronic component with high reliability, a manufacturing method of the electronic component, and a manufacturing method of an electronic circuit device.
Requests for downsizing, lightening and thinning a portable information terminal such as a portable telephone have recently increased, and thus much related technological development has been performed. An electronic component including a semiconductor component must be therefore downsized and lightened, and an electronic circuit device employing it must be also downsized, lightened, and thinned. Since the electronic component is downsized, area of a connection part between an electrode of the electronic component and a connection terminal of a circuit board decreased. Therefore, new technology is required for securing reliability of the connection part.
A chip scale package (CSP) structure has been developed for downsizing and thinning the semiconductor component, and this technology has been applied to not only the semiconductor component but also a high frequency electronic component.
A peculiar structure and a manufacturing method are developed for the semiconductor component having the CSP structure. For example, Japanese Patent Laid-Open No. 9-237806 and Japanese Patent Laid-Open No. 11-274241 disclose a method of manufacturing such semiconductor components, and a method of connecting these semiconductor components to a circuit board. In this manufacturing method, projection electrodes such as solder bumps or gold ball bumps are formed on connection electrodes of semiconductor components, a resin film for wholly covering the projection electrodes is then formed, the resin film is cured, the surface of the resin film is then polished to expose the surfaces of the projection electrodes, and a semiconductor wafer is divided into the individual semiconductor components. These methods allow extreme thinning and downsizing of the semiconductor components comparing with a semiconductor component having the CSP structure formed by a conventional resin mold method.
Additionally, Japanese Patent Laid-Open No. 9-246905 discloses an electronic component including a surface acoustic wave element. The electronic component includes projection electrodes formed on connection electrodes of the surface acoustic wave element and a lid body for covering an active region of the elastic wave element. This publication also discloses a circuit board on which the electronic component is assembled, and a protective resin for covering the lid body.
A conventional electronic component, a method of manufacturing the electronic component, and a method of manufacturing an electronic circuit device employing it will be described hereinafter with reference to FIG. 8A to FIG. 8E and FIG. 9.
FIG. 8A through FIG. 8E are sectional views used for illustrating a conventional manufacturing method of the electronic component such as a semiconductor component and the electronic circuit device.
In FIG. 8A, large number of semiconductor components (not shown) including circuit elements such as transistors and resistors are formed on a semiconductor wafer 30A, and projection electrodes 31 are formed on connection electrodes (not shown) of the semiconductor components. The semiconductor wafer 30A will be subsequently divided into individual semiconductor components along cutting lines 32.
In FIG. 8B, a resin film 33 is formed over the whole surface of the wafer 30A by a spin coat method so as to wholly cover the projection electrodes 31. The surface of the resin film 33 formed on the main surface of the wafer 30A is then polished or ground, thereby exposing the tip surfaces 34 (hereinafter called top parts) of the projection electrodes 31 as shown in FIG. 8C. Then, the wafer 30A is diced along the cutting lines 32, and thus divided into individual semiconductor components 35.
Then, in FIG. 8D, a circuit board 36 having connection terminals 37 and internal wiring 38 is prepared. A vacuum chuck 39 sucks and holds a semiconductor component 35 and positions the projection electrodes 31 onto the connection terminals 37. Ultrasonic wave is supplied to the vacuum chuck 39 to bond the projection electrodes 31 to the connection terminals 37.
In FIG. 8E, a resin film 40 covers and protects at least a peripheral part of the semiconductor component 35. The resin film 40 may wholly cover the semiconductor component 35.
FIG. 9 is a sectional view of an essential part of an electronic circuit device employing an electronic component having a surface acoustic wave element. Internal wiring 42 and connection terminals 43 are formed on a circuit board 41. The electronic component 44 has the surface acoustic wave element (not shown), and a lid body 46 covers an active region of the surface acoustic wave element and thereby forms a vibration space. A resin film 47 covers them.
The electronic component having the surface acoustic wave element is manufactured by the following processes:
Forming many surface acoustic wave elements on a piezoelectric wafer;
Forming a lid body 46 to cover an active region of each surface acoustic wave element and forms a vibration space;
Forming projection electrodes 45 on connection electrodes; and
Dividing the wafer into individual electronic components.
The projection electrodes 45 of each of the electronic components 44 manufactured by this method are positioned onto the connection terminals 43 on the circuit board 41, and then ultrasonic wave is applied to the electronic component to bond the projection electrodes 45 to the connection terminals 43. Then, the resin film 47 covers the peripheral part or the whole of the electronic component 44, thereby forming the electronic circuit device having the surface acoustic wave element.
In a conventional method of manufacturing a semiconductor component, projection electrodes are formed, the surface of a wafer is coated with resin, and the resin is polished or ground to expose the surfaces of the projection electrodes. The resin film formed on the wafer with a diameter as large as 20 cm is hardly polished or ground uniformly, and a number of processes increases.
The semiconductor components must be stored so as to prevent the top parts of the projection electrodes from being contaminated since the wafer is divided into individual semiconductor components with the top parts of the projection electrodes exposed until the semiconductor components are mounted on the circuit boards. The projection electrodes, upon being made of easily-oxidized metal other than gold, have respective surfaces oxidized.
Methods of manufacturing a conventional electronic component having a surface acoustic wave element and a conventional electronic circuit device also have a problem similar to that of the semiconductor component discussed above. In a method of mounting the electronic component on the circuit board and then protecting the peripheral part with resin, a lid body must be carefully handled because strength of the lid body may be not sufficient in the previous processes.
Additionally, the surface acoustic wave element includes an inter-digital transducer (IDT) electrode and a connection electrode that are made of aluminum film on the main surface of a piezoelectric substrate. The aluminum film is exposed in other region than the region covered with the lid body. A gold ball bump as the projection electrode is formed on the connection electrode made of the aluminum film. Coolant is poured onto the wafer in a dicing process, but the coolant may cause corrosion of the electrode or penetration of water into the lid body.
When LiTaO3 or LiNbO3 is used as a piezoelectric wafer, powder generated during dicing may alkalinize the coolant, which may corrode the aluminum film. When the gold ball bump is formed on the connection electrode made of the aluminum film, electrochemical corrosion may occur on the interface between them.
An electronic component has not only a top part of a projection electrode but also the main surface mechanically and environmentally protected. A method of manufacturing the electronic component and a method of manufacturing an electronic circuit device employing the electronic component are provided.
The electronic component includes a substrate, a circuit element disposed on the substrate, a connection electrode connected to the circuit element disposed on the substrate, a projection electrode formed on the connection electrode, and a protective film for covering the circuit element, the substrate, and the projection electrode.